Excess electrical energy, which originates from renewable energy sources, for example, may only be stored in the power network to a limited extent. This also applies to excess energy which arises in fossil fuel power plants when they are running in the optimally cost-effective load range, but is not retrieved from the network by the consumer. There are various large-scale storage devices for the temporary storage of this excess energy in large quantities. One of these is, for example, a pumped-storage power plant. In the battery sector, one approach for an electrical energy store is to use so-called rechargeable oxide batteries (ROB), i.e., high-temperature metal-air batteries. In these batteries, a storage medium is reduced or oxidized depending on the battery state (charging or discharging). During a plurality of these cyclic charging (i.e., reduction) and discharging (i.e., oxidation) operations of the storage medium, this medium has the tendency in the case of the applied, comparatively high operating temperatures of such a battery, which are typically between 600° C. and 900° C., that the required microstructure, in particular the pore structure of the storage medium, is impaired by sintering processes. This results in aging and subsequently failure of the battery.